Can't open Yahoo mail in IE11 / Windows 8.1

When I go to my Yahoo mail page, it doesn't respond to any key clicks - I can't open any item of mail, nor any of the various links down the left hand side of the mail page.

As far as I can tell, other Yahoo things (all of the applications which appear above the mail's main window) work correctly, including links within those applications.

Yahoo mail works correctly in both Chrome and Firefox.

Why does it no longer work in IE11 ?

 

I believe the problem is with Internet Explorer as I have exactly the same issue with IE9 in Windows 7. It's so slow that it seems unresponsive. I have to wait minutes at a time to go from reading an email to deleting emails. In Mozilla Firefox everything works fine.
I now check my Yahoo Mail using Mozilla Firefox, or I receive the messages with EssentialPIM.

 

Thank you Eldon.

Since posting the question I have had to refresh Windows 8.1 and that has cleared the problem. Not very satisfactory since I don't know what was causing it.